JP2009041456A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine capable of detecting leakage of exhaust gas from an upstream side connecting tube of a differential pressure sensor in a particulate filter and estimating the leakage amount to correct an estimated value of particulate matter accumulating amount to the particulate filter. <P>SOLUTION: The control device for the internal combustion engine calculates, based on two exhaust gas flow rates and estimated values of the particulate matter accumulating amount acquired within a predetermined time, a difference between the accumulating amount estimated value with the larger exhaust gas flow rate and the accumulating amount estimated value with the smaller exhaust gas flow rate. When the difference is larger than a predetermined threshold value, a determination means determines that exhaust gas is leaked from the upstream side connecting tube 10 of the diesel particulate filter (DPF) 6. Moreover, the control device estimates the leakage amount, and performs lighting of a warning lamp 14 and change in EGR amount by an EGR valve 13 etc. in accordance with the degree of the leakage amount. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine.

  In the recent trend of emphasizing environmental protection, technology for purifying exhaust from internal combustion engines mounted on automobiles and the like is essential. For example, in a diesel engine, it is necessary to remove exhausted particulate matter (PM, particulate matter) from the exhaust. For this purpose, a diesel particulate filter (DPF) is usually provided in the middle of the exhaust pipe.

  Most of the DPFs are so-called honeycomb-structured filters, and most of the PM discharged from the engine is collected by the filters, thereby achieving the purpose of exhaust purification. However, when the DPF is used, every time PM is collected in the DPF to some extent, the DPF must be regenerated by burning the collected PM.

  In order to regenerate the DPF at an appropriate time, it is desirable to accurately estimate the amount of PM accumulated in the DPF, and to regenerate the DPF when the estimated value exceeds a predetermined value. As a method for estimating the PM deposition amount of the DPF, there is a method for estimating the PM deposition amount from the differential pressure (or DPF differential pressure) that is the difference between the exhaust pressure on the inlet side and the outlet side of the DPF and the exhaust gas flow rate. When the differential pressure of the DPF is measured for this method, a pipe for guiding pressure (hereinafter referred to as a pressure guiding pipe) is formed from the inlet side and the outlet side of the DPF up to the differential pressure sensor, and the differential pressure sensor is used for the inside of both the pressure guiding pipes. Measure the pressure difference.

  The pressure guiding pipe is a heat-resistant metal pipe or rubber hose, but if damage such as cracking or disconnection occurs depending on the use environment, the exhaust leaks to the outside. When leakage occurs from the pressure guiding pipe, the detected value of the differential pressure decreases, and the estimated PM accumulation amount decreases from the true value. Therefore, there is a risk that the DPF regeneration timing is delayed and the temperature rises excessively during regeneration. For this reason, it is necessary to detect the occurrence of leakage from the pressure guiding tube and take appropriate measures.

  For example, the following Patent Document 1 discloses a technique for determining that a pressure guide tube is damaged when the pulsation width of the DPF differential pressure is equal to or greater than a predetermined value as a method for detecting the pressure guide tube breakage of the DPF.

JP 2005-226519 A

  The breakage determination technique disclosed in Patent Document 1 is suitable for detecting breakage of the pressure guiding tube on the downstream side of the DPF with respect to the differential pressure sensor. On the other hand, the damage in the DPF upstream side pressure guiding tube is more problematic from the viewpoint of exhaust purification because the exhaust gas before PM is collected by the DPF leaks to the outside.

  Further, there may be a situation in which the internal combustion engine must be continuously operated even when a leak occurs when the leak amount is small. In such a case, it is preferable to correct the estimated DPM amount of the DPF according to the leakage amount while estimating the leakage amount, so that DPF regeneration can be performed at an appropriate time despite the leakage.

  Therefore, in view of the above problems, the problem to be solved by the present invention is that when exhaust gas leaks from the upstream pressure guiding pipe of the differential pressure sensor in the particulate filter, this can be detected and the amount of leakage is estimated. Another object of the present invention is to provide a control device for an internal combustion engine that can correct the estimated value of the amount of particulate matter deposited on the particulate filter.

Means for Solving the Problems and Effects of the Invention

  In order to achieve the above object, a control apparatus for an internal combustion engine according to a first aspect of the present invention includes a particulate filter that collects particulate matter in exhaust gas and an inlet portion of the particulate filter in an exhaust passage. The difference between the internal pressures of the upstream pressure guiding pipe, which is the pipe, the downstream pressure guiding pipe, which is the pipe formed from the outlet portion of the particulate filter, and the upstream pressure guiding pipe and the downstream pressure guiding pipe. A control device for an internal combustion engine comprising a differential pressure sensor for measuring a differential pressure, the detection means for detecting an exhaust flow rate discharged from the internal combustion engine, and the differential pressure measured by the differential pressure sensor And first estimation means for estimating the amount of particulate matter deposited on the particulate filter from the exhaust flow rate detected by the detection means, and the internal combustion engine is operated. Two different times are defined as a first time and a second time, and the interval between the first time and the second time is within a predetermined time. At the first time, the detection means The detected exhaust flow rate is set as a first flow rate, the accumulation amount estimated by the estimation unit is set as a first estimated value, and the exhaust flow rate detected by the detection unit at the second time is set as a first flow rate. The first estimated value and the second estimated value are assumed to be a flow rate of 2, assuming that the accumulation amount estimated by the estimating means is a second estimated value, and that the second flow rate is larger than the first flow rate. And determining means for determining that there is a gas leak from the upstream pressure guiding tube when the difference from the value is greater than a predetermined threshold value.

  As a result, the difference between the estimated exhaust gas flow rate with the larger exhaust gas flow rate and the estimated exhaust gas flow rate with the smaller exhaust gas flow rate is obtained from the two exhaust gas flow rates and the estimated particulate matter accumulated gas amount acquired within the predetermined time. When this difference is larger than the predetermined threshold value, it can be determined by the determining means that the exhaust gas is leaking from the upstream guiding tube of the particulate filter. If there is a leak from the upstream impulse line, the exhaust will be discharged to the outside before the particulate matter is collected by the particulate filter. Therefore, whether or not it leaks from the upstream impulse line is useful for exhaust purification. Information. This useful information can be obtained by the present invention.

  The second estimation means for estimating the amount of particulate matter deposited on the particulate filter from the operating state of the internal combustion engine, and the predetermined threshold value is increased as the estimated value by the second estimation means increases. And a changing unit.

  As a result, the amount of particulate matter deposited on the particulate filter is estimated by the second estimating means, and the larger the estimated value, the larger the predetermined threshold value by the changing means. In comparison, it is possible to determine the damage of the upstream pressure guiding tube more precisely. In particular, since the difference between the second estimated value and the first estimated value tends to increase as the estimated value by the second estimating means increases, the upstream side can be increased by increasing the predetermined threshold in such a case. The possibility of determining that the pressure guiding tube is accidentally damaged can be reduced.

  Further, after the determination means determines that there is a gas leak from the upstream pressure guiding tube, an estimation method selection means for estimating the accumulation amount using only the second estimation means may be provided.

  Thus, after the determination means determines that there is a gas leak from the upstream pressure guiding tube, the deposition amount is estimated using only the second estimation means, so the deposition amount is estimated without being affected by the leakage. be able to. Therefore, the accuracy of estimation of the deposition amount is improved, and the particulate filter regeneration time can be appropriately determined.

  A second estimation unit configured to estimate a deposition amount of the particulate matter of the particulate filter from an operating state of the internal combustion engine, and the predetermined amount of time estimated by the second estimation unit; The estimated value may be the time for the predetermined accumulation amount to increase.

  As a result, the time during which the estimated value of the accumulation amount estimated by the second estimating means increases by the predetermined accumulation amount is set as the predetermined time, so that the upstream side pressure guiding tube is more accurate than when the predetermined time is constant. Can be judged. When the accumulation amount increase rate is slow, such as during low-speed operation, the predetermined time becomes longer. Therefore, the predetermined time is too short and the difference between the second estimated value and the first estimated value is small, so that no damage is erroneously detected. The possibility can be reduced. In addition, when the accumulation amount increase rate is fast, such as during high-speed operation, the predetermined time is shortened. Therefore, the predetermined time is too long, and the difference between the second estimated value and the first estimated value becomes large, and it is erroneously determined as damaged. The possibility is reduced.

  A control device for an internal combustion engine according to a second aspect of the present invention includes a particulate filter that collects particulate matter in the exhaust gas in an exhaust passage, and an upstream pressure guiding tube formed from an inlet portion of the particulate filter. An internal combustion engine including a downstream pressure guiding tube formed from an outlet portion of the particulate filter, and a differential pressure sensor for measuring a differential pressure which is a difference in pressure between the upstream pressure guiding tube and the downstream pressure guiding tube An engine control apparatus, comprising: a detection unit that detects an exhaust flow rate discharged from the internal combustion engine; the differential pressure measured by the differential pressure sensor; and the exhaust flow rate detected by the detection unit. First estimating means for estimating the amount of the particulate matter deposited on the particulate filter, and two different times when the internal combustion engine is operating are designated as a first time and a second time. The interval between the first time and the second time is within a predetermined time. At the first time, the exhaust flow rate detected by the detection means is set as a first flow rate, and the estimation means The estimated accumulation amount is set as a first estimated value, the exhaust flow rate detected by the detection means at the second time is set as a second flow rate, and the accumulation amount estimated by the estimation means is set as a first flow rate. As the estimated value of 2, assuming that the second flow rate is larger than the first flow rate, the first flow rate, the second flow rate, the second estimated value, and the first estimated value A leakage amount estimating means for estimating a leakage amount of gas from the upstream pressure guiding tube from the difference is provided.

  As a result, the leakage amount estimation means determines the amount of gas leakage from the upstream impulse line from the difference between the first flow rate, the second flow rate, and the second estimated value and the first estimated value. presume. If there is a leak from the upstream impulse line, exhaust will be discharged outside before the particulate matter is collected in the particulate filter, so how much leakage from the upstream impulse line is useful for exhaust purification. Information. This useful information can be obtained by the present invention.

  Further, from the operating state of the internal combustion engine, the second estimation means for estimating the amount of particulate matter deposited on the particulate filter, the second flow rate, and the leakage amount estimated by the leakage amount estimation means And a correction unit that corrects the estimated value of the accumulation amount estimated by the second estimation unit.

  As a result, the accumulated amount estimated value obtained by the second estimating means is corrected from the second flow rate and the leakage amount estimated by the leakage amount estimating means by the correcting means. The value can be determined. Therefore, it is possible to determine the regeneration timing of the particulate filter more appropriately by using a more accurate accumulated amount estimation value.

  Also, a warning light for warning, EGR for recirculation of exhaust gas, and lighting of the warning light when the leakage amount estimated by the leakage amount estimation means is larger than a first predetermined leakage amount, the EGR amount Or a first control means for performing at least one of the change of the injection pressure of the internal combustion engine.

  Accordingly, when the leakage amount estimated by the leakage amount estimation means is larger than the first predetermined leakage amount, a warning by a warning lamp, a change in the EGR amount, or a change in the injection pressure of the internal combustion engine is performed. Therefore, the warning by the warning light can warn the driver of the occurrence of leakage, and can prompt the driver to take appropriate measures. Further, in the change of the EGR amount, the exhaust amount of particulate matter from the internal combustion engine can be suppressed by changing the EGR amount in a situation where the exhaust gas containing the particulate matter is leaking from the upstream pressure guiding tube. Thereby, the reduction of the exhaust purification performance due to leakage can be suppressed. Further, even when the injection pressure of the internal combustion engine is changed, the discharge of particulate matter from the internal combustion engine can be reduced. Therefore, it is possible to suppress a reduction in exhaust purification performance due to leakage.

  Further, the second predetermined leakage amount is larger than the first predetermined leakage amount, and when the leakage amount estimated by the leakage amount estimation means is larger than the second predetermined leakage amount, the rotational speed of the internal combustion engine, the intake pressure, At least one of the intake amount, the exhaust pressure, the exhaust temperature, and the exhaust leakage amount may be set to a predetermined value or less, or the regeneration of the particulate filter may be prohibited.

  Thereby, when the leakage amount estimated by the leakage amount estimation means is larger than the second predetermined leakage amount, it is determined that the leakage amount is extremely large, and the engine speed, intake pressure, intake amount, exhaust pressure, At least one of the exhaust temperature and the amount of exhaust leakage is set to a predetermined value or less, or regeneration of the particulate filter is prohibited. Therefore, by setting at least one of the rotational speed of the internal combustion engine, the intake pressure, the exhaust pressure, the exhaust temperature, and the exhaust leakage amount to a predetermined value or less, the exhaust amount from the internal combustion engine is suppressed, and as a result, the particulate matter is discharged. Since the amount is also suppressed, exhaust deterioration due to the influence of leakage is suppressed. Further, by prohibiting the regeneration of the particulate filter, it is possible to avoid further leakage in a state where the temperature is raised by the regeneration.

  Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 1 is a schematic diagram of a first embodiment of a control device 1 for an internal combustion engine according to the present invention.

  It is assumed that the control device 1 is configured for a four-cylinder diesel engine 2 (hereinafter simply referred to as an engine). An intake pipe 3 is connected to the engine 2, and air is supplied from the intake pipe 3 to the engine 2. Exhaust gas is discharged to an exhaust pipe 5 connected to the engine 2. Various controls including fuel injection of the engine 2 are performed by the electronic control unit 9 (ECU). The intake pipe 3 is equipped with an air flow meter 4 to measure the intake amount (flow rate per unit time).

  A diesel particulate filter 6 (DPF) is disposed in the middle of the exhaust pipe 5. A differential pressure sensor 7 for measuring a differential pressure, which is a difference in exhaust pressure between the inlet side and the outlet side of the DPF 6, is also provided. Exhaust gas is guided by an upstream pressure guiding tube 10 (pressure guiding tube) formed from the inlet side of the DPF 6 toward the differential pressure sensor 7 for the differential pressure sensor 7, and also toward the differential pressure sensor 7 from the outlet side of the DPF 6. A downstream pressure guiding tube 11 (pressure guiding tube) is formed to guide the exhaust. The differential pressure sensor 7 measures the difference in the exhaust pressure in the pressure guiding tubes 10 and 11. The measured values of the differential pressure sensor 7 and the air flow meter 4 are sent to the ECU 9.

  For example, the DPF 6 has a typical structure in which the inlet side and the outlet side are alternately packed in a so-called honeycomb structure. The exhaust discharged during operation of the engine 2 contains particulate matter (PM), and this PM is collected inside or on the surface of the filter wall when the exhaust gas passes through the filter wall having the above structure of the DPF 6. Is done. Every time the amount of PM deposited on the DPF 6 becomes sufficiently large, the deposited PM must be removed by burning to regenerate the DPF 6. As a method for regenerating the DPF 6, there is post-injection in which fuel injection is performed at the timing after the main injection in the engine 2.

  The engine 2 is equipped with an EGR (Exhaust Gas Recirculation) passage 12 for returning exhaust gas to the intake pipe 3. An EGR valve 13 is disposed on the passage 12, and the amount of EGR increases or decreases depending on the opening degree. An intake throttle valve 15 is disposed in the intake pipe 3, and the intake air amount increases or decreases depending on the opening degree. The opening degrees of the EGR valve 13 and the intake throttle valve 15 are controlled by the ECU 9. A warning lamp 14 is also provided for informing the driver of exhaust gas leakage, which will be described later.

  As described above, an object of the present invention is to detect when the upstream pressure guiding tube 10 of the DPF 6 is damaged and gas leaks. The basic procedure for this is to estimate the PM accumulation amount in the DPF 6 (at least) twice under different exhaust flow rates within a predetermined time, and when the difference in the accumulation amount is too large, the upstream side pressure guiding tube 10 It is determined that there is damage and there is a gas leak.

  In the following, two types of estimation of the PM deposit amount in the DPF 6 are performed. One is a method for estimating from the differential pressure of the DPF 6, and this is referred to as a PM deposit amount estimation A, an estimation method A, a method A, and the like. Is an estimated PM deposit amount A or the like. The other method is to estimate from the operation history of the engine 2, which is PM deposition amount estimation B, estimation method B, method B, etc., and the estimated value by this method is PM deposition amount estimation value B or the like.

  Method A will be described more specifically. In general, the amount of PM accumulated in the DPF 6 is determined by the differential pressure of the DPF 6 and the exhaust gas flow rate (flow rate per unit time) flowing into the DPF 6. This is shown in FIG. When points with the same PM deposition amount are plotted on a plane having the DPF differential pressure and the exhaust gas flow rate as coordinate axes, an equal deposition amount line as shown in FIG. 15 is obtained.

  In Method A, the DPF differential pressure is measured by the differential pressure sensor 7. The amount of exhaust gas flowing into the DPF 6 is assumed to be equal to the amount of intake air supplied to the engine 2, and the measured value of the air flow meter 4 is set as the value of the exhaust gas flow rate. Then, it is observed on which equal deposition amount line the points formed by these measured values are on the plane of FIG. Thereby, the estimated value of the PM accumulation amount is obtained. Actually, the plane in FIG. 15 may be finely divided into meshes, and the PM deposition amount may be obtained for each region.

  Next, method B will be described. In Method B, the PM accumulation amount is calculated from the history of the operating state of the engine 2. The operating state of the engine 2 is represented by the point on the plane having the rotation speed and the load (or fuel injection amount) as coordinate axes as shown in FIG. In the method B, this plane is divided into fine meshes as shown in FIG. 16, and the amount of PM discharged from the engine 2 per unit time is obtained and stored in each region by an experiment or the like. Then, according to the change in the operation state from the start of operation, this plane is traced and the PM amount in the area that has passed is accumulated. In the method B, it is assumed that all PM discharged from the engine 2 is collected in the DPF 6, and this integrated value is set as an estimated value of the PM accumulation amount in the DPF 6.

  A flowchart of the DPF pressure guiding tube breakage detection process is shown in FIG. The processing procedure of FIG. 2 is incorporated in a part (S310) of the flowchart of FIG. 3 to be described later.

  First, FIG. 2 will be described. In the following description, a variable n is used. This is a variable indicating whether the first or second estimation of the PM deposition amount twice within the predetermined time described above. As the first procedure of this process, the ECU 9 determines whether or not the value of the variable n is 1 in S10. That is, it is a determination as to whether or not the first PM accumulation amount is estimated.

  If it is the first estimation (S10: YES), the process proceeds to S20. If it is the second estimation (S10: NO), the process proceeds to S30. In S20, the timer is reset and started (or restarted). It is assumed that this timer is built in the ECU 9. By this timer, it is determined whether it is within a predetermined time as described above. The predetermined time is set in advance.

  Next, in S30, it is determined whether it is within a predetermined time. If it is within the predetermined time (S30: YES), the process proceeds to S40, and if the predetermined time has passed (S30: NO), the process proceeds to S110. In S110, the value of the variable n is set to 1, and this process is terminated.

  In S40, the exhaust flow rate is measured. In this embodiment, the exhaust flow rate is replaced with the intake air amount to the engine 2. The intake air amount is measured by the air flow meter 4. That is, in S40, the intake air amount measured by the air flow meter is sent to the ECU 9. Next, in S50, the PM accumulation amount in the DPF 6 is estimated by the method A described above.

  Next, in S60, it is determined whether or not the variable n is 1. When the variable n is 1, that is, when that time is the first estimation within the predetermined time (S60: YES), the exhaust flow rate measured in S40 is stored in the variable VEX1 in S70 and estimated in S50. The PM accumulation amount estimated value A is stored in the variable PM1 in S90.

  On the other hand, when the variable n is 2, that is, when that time is the second estimation within the predetermined time (S60: NO), the exhaust flow rate measured in S40 is stored in the variable VEX2 in S80 and estimated in S50. The estimated PM deposition amount A is stored in the variable PM2 in S100.

  When S90 ends, the process for the first estimation is completed, so the value of variable n is changed to 2 in S120, and this series of processes ends. When S100 ends, the process proceeds to S130. The time point of proceeding to S130 is the second estimation (therefore, the value of n is 2), and all the above VEX1, VEX2, PM1, and PM2 have already been obtained.

  In S130, S140, and S150, basically, the difference between PM1 and PM2 obtained above is obtained. In this case, one of PM1 and PM2 has a larger exhaust flow rate from a value corresponding to a smaller exhaust flow rate. Subtract the value corresponding to. If the difference is larger than the predetermined value, it is determined that there is a gas leak due to damage to the upstream pressure guiding tube 10 (hereinafter simply referred to as a pressure guiding tube) of the DPF 6. Strictly speaking, the magnitudes of VEX1 and VEX2 are compared in S130, and if VEX2 is larger (S130: YES), it is determined in S140 whether PM1-PM2 is equal to or smaller than a predetermined value Δ1.

  If Δ1 or less (S140: YES), this process ends. When larger than Δ1 (S140: NO), the process proceeds to S160. If VEX1 is equal to or greater than VEX2 (S130: NO), it is determined in S150 whether PM2-PM1 is equal to or less than Δ1. If Δ1 or less (S150: YES), this process ends. When larger than Δ1 (S150: NO), the process proceeds to S160. In S160, it is determined that the pressure guiding tube of the DPF 6 is broken.

  The meaning of the processing procedure in FIG. 2 will be described below with reference to FIGS. First, FIG. 8 shows the relationship between the amount of intake air supplied to the engine 2 and the gas flow rate passing through the DPF 6 in the case where there is a leak in the pressure guiding tube 10 of the DPF 6. When there is no leakage, the intake air amount and the DPF passage gas flow rate can be regarded as substantially equal as indicated by the dotted line.

  When there is a leak in the pressure guiding tube, the DPF passage gas flow rate becomes smaller than the intake air amount due to the leak, and as shown by the solid line, the larger the leak, the lower the solid line in the figure. According to the knowledge obtained by the inventor, the amount of decrease due to leakage tends to increase as the intake air amount or the DPF gas flow rate increases with respect to an arbitrary leakage amount. This shows that the decrease v2 due to leakage in FIG. 8 is larger than the decrease v1.

  The influence of such a tendency of leakage on the estimation of the PM accumulation amount will be described with reference to FIG. FIG. 9 shows the relationship between the differential pressure of the DPF 6 and the exhaust gas flow rate for different PM accumulation amounts. FIG. 9 illustrates solid lines 110, 120, and 130 indicating PM accumulation amounts of 10, 9, and 5 grams. In order to make the following explanation easy to understand, it is assumed that the amount of accumulated PM is constant at 10 grams within a predetermined time in this embodiment. It is assumed that there is a leak from the pressure guiding tube 10.

  In the above embodiment, the true value in the first estimation of the PM accumulation amount is point 101, and the true value in the second estimation of the PM accumulation amount is point 102. That is, at the time of the first estimation, the DPF differential pressure is ΔP1, and the flow rate of the exhaust gas flowing into the DPF 6 is VEX3. At the time of the second estimation, the DPF differential pressure is ΔP2, and the flow rate of the exhaust gas flowing into the DPF 6 is VEX4.

  However, as described above, in the present embodiment, the flow rate of the exhaust gas flowing into the DPF 6 is not directly measured, but is replaced by the measured value of the intake air amount by the air flow meter 4 on the upstream side of the engine 2. Therefore, when the leakage is taken over from FIG. 8 and indicated by v 1 and v 2, when the true value is the point 101 as shown in the drawing, the intake air amount measured by the air flow meter 4 is VEX 1, and thus the measured value is the point 103.

  Similarly, when the true value is the point 102, the intake air amount measured by the air flow meter 4 is VEX2, and thus the measured value is the point 104. Since the point 103 is on the solid line 120 where the PM deposition amount is 9 grams, the first PM deposition amount estimation value PM1 is 9 grams (not 10 grams which is the true value). Since the point 104 is on the solid line 130 where the PM deposition amount is 5 grams, the second PM deposition amount estimated value PM2 is 5 grams (not 10 grams which is the true value). In this embodiment, if 4 grams, which is the difference between 9 grams and 5 grams, is greater than a predetermined value (Δ1), it is determined that the pressure guiding tube 10 is broken.

  To summarize the above, when the PM accumulation amount is estimated at two times when the exhaust gas flow rate is different, the true value at two times in FIG. 9 due to the difference in leakage amount (difference between v1 and v2) shown in FIG. Are the points on the same PM deposit (10 grams), the estimated values are different at each time (5 grams and 9 grams). Naturally, when there is no leakage, the PM accumulation amount estimated value is 10 grams at both times, and there is no difference. In the flowchart of FIG. 2 described above, the difference between the PM accumulation amount estimated values at two times is obtained by using such a property, and it is determined whether there is a leak based on whether or not this difference is larger than a predetermined threshold value. The above is the meaning of the processing of FIG.

  In the above, for the sake of simplification, the discussion has been made on the assumption that the true value of the PM deposition amount is constant within a predetermined time. However, in general, PM is deposited every moment, so this assumption is not strictly established. However, in the present invention, two times are limited to a predetermined time, and there is an upper limit to an increase in the amount of newly deposited PM within the predetermined time. Therefore, the threshold value Δ1 may be set in consideration of this upper limit. In that case, if the PM deposition amount fluctuates so as to be impossible considering this upper limit, it can be determined that the pressure guiding tube 10 of the DPF 6 is damaged. That is, the flowchart of FIG. 2 is effective even when the true value of the PM deposition amount is not constant.

  The reason why VEX1 and VEX2 are determined in S130 and the subsequent processing is divided into S140 and S150 is based on the tendency of the leakage described above. PM2 tends to be larger than PM1, and when VEX2 is larger than VEX1, PM1 becomes larger than PM2 due to leakage. Therefore, in S140 and S150, the smaller value is subtracted from the larger value.

  As described above, the flowchart of FIG. 2 is used in S310 of the flowchart of FIG. The flowchart of FIG. 3 will be described below.

  Since PM accumulates in the DPF 6 as the engine 2 is operated, the accumulated PM is burned and the DPF 6 is regenerated when the accumulation amount exceeds a predetermined value. The flowchart in FIG. 3 is a process for determining the regeneration time of the DPF 6. The flowchart of FIG. 3 may be periodically performed according to a predetermined cycle, for example.

  In this process, it is first determined whether or not it is determined in S300 that the pressure guiding tube 10 of the DPF 6 is damaged. Of course, this determination is not made at the start of operation of the engine 2. While the determination is not made (S300: NO), the process proceeds to S310.

  If the operation is continued and the flowchart of FIG. 3 is repeatedly processed to make the same determination in S310 described later (S300: YES), the process proceeds to S320. While the determination is not made, the process always proceeds to S310. Once the determination is made, the process always proceeds to S320. However, if damage to the pressure guiding tube is repaired, the determination is reset to a state where there is no such determination.

  In S310, processing for detecting whether or not the pressure guiding tube 10 of the DPF 6 is broken is performed. This procedure is the flowchart of FIG. 2 described above. That is, in S310, the procedure from S10 to S160 is processed.

  Next, in S330, the PM accumulation amount estimated value A obtained in S310 is stored in the variable PM. When the process proceeds to step S320, the PM accumulation amount in the DPF 6 is estimated by the method B described above. Then, the estimated value B is stored in the variable PM in the next S340. After S330 or S340, the process proceeds to S350.

  In S350, it is determined whether or not the value of the variable PM obtained in S330 or S340 is larger than a predetermined value. If it is equal to or greater than the predetermined value (S350: YES), it is determined that the amount of accumulated PM has exceeded the allowable range, PM is combusted in S360, and regeneration of the DPF 6 is executed. When the reproduction ends, this processing procedure ends. If the amount of accumulated PM is smaller than the predetermined value (S350: NO), the processing procedure is terminated without performing DPF regeneration.

  According to the processing procedure of FIG. 3, when there is a damage determination on the DPF 6 pressure guiding tube 10, the process always proceeds to S320 and S340, and thereafter, S310 damage detection is not performed, and the PM deposition amount is determined using only method B. presume. Therefore, it is possible to regenerate the DPF 6 at an appropriate time by using an accurate estimated amount of deposit by Method B that is not affected by leakage.

  Next, Example 2 will be described. The second embodiment is the same as the first embodiment except that the flowchart of FIG. 2 in the first embodiment is replaced with FIG. 4. In the second embodiment, the PM accumulation amount estimation B is incorporated into the DPF pressure guiding tube breakage detection process, and the value of Δ1 is changed according to the estimated value B obtained thereby. As a result, more accurate damage determination is performed than when Δ1 is a constant value. Only parts of the second embodiment different from the first embodiment will be described below.

  In the flowchart of FIG. 4, the procedures of S55 and S56 are added to FIG. Others are the same as FIG. In S55, PM accumulation amount estimation B is performed. Then, according to the estimated value B, the value of Δ1 is changed in S56. The change here is performed under the regularity that Δ1 increases as the estimated value B increases. The specific relationship between the estimated value B and the value of Δ1 may be determined appropriately for the device configuration to be used in advance and stored in the ECU 9 in the form of a map or the like. Using this map, the value of Δ1 is determined in S56.

  The reason why the change of the value of Δ1 in S56 is effective will be described below with reference to FIGS. FIG. 10 is a diagram in which the influence of leakage from the pressure guiding tube 10 is added to FIG. First, assume that the state of the DPF 6 is at a point 201. That is, the DPF differential pressure is ΔPa, the exhaust gas flow rate is VEXa, and the PM deposition amount is PMa. Here, it is assumed that the pressure guiding tube 10 is broken and leakage occurs.

  Assuming that the leakage amount is v3 and the PM accumulation amount does not change, the point moves to the point 202 as shown in FIG. That is, the DPF differential pressure decreases to ΔPb, and the exhaust gas flow rate flowing into the DPF 6 decreases to VEXb. However, as described above, in this embodiment, the flow rate of gas flowing into the DPF 6 is the same as the intake air amount measured by the air flow meter 4. Since the air flow meter 4 is upstream of the engine 2, it is not affected by leakage from the pressure guiding tube 10. Therefore, the exhaust gas flow rate is kept at VEXa and is regarded as a movement to the point 203. At this point 203, the PM accumulation amount is on the PMb line, so the PM accumulation amount estimated value is changed to PMb.

  Next, the same discussion is repeated with the point 204 as a starting point. As a result, the point 204 is moved to the point 205, but is regarded as the point 206 from the measured value. The DPF differential pressure decreases from ΔPc to ΔPd. The important point is that the difference between ΔPa and ΔPb is larger than the difference between ΔPc and ΔPd. That is, when the amount of leakage is the same, the amount of decrease in the DPF differential pressure is larger as the PM accumulation amount is larger.

  Next, the process moves to FIG. FIG. 11 is a rewrite of FIG. 15 with the relationship between the DPF differential pressure and the PM deposition amount (estimated value) under the condition that the exhaust gas flow rate is constant. Under the condition that the exhaust gas flow rate is constant, the relationship between the DPF differential pressure and the PM deposition amount is represented by a solid line 300 including two straight lines as shown in FIG. ΔPa, ΔPb, ΔPc, and ΔPd in FIG. 10 are written on the vertical axis in FIG.

  Points on the solid line 300 whose DPF differential pressure values are ΔPa, ΔPb, ΔPc, and ΔPd are designated as points 301, 302, 303, and 304, respectively. From the above discussion, PMa, PMb, PMc, and PMd are PM deposition amounts at the points 301, 302, 303, and 304, respectively. As described above, the difference between ΔPa and ΔPb is larger than the difference between ΔPc and ΔPd. From this fact and the shape of the solid line 300, it can be concluded that the difference between PMa and PMb is larger than the difference between PMc and PMd.

  That is, when the amount of leakage is the same, the amount of decrease in the estimated amount of accumulated PM increases as the amount of accumulated PM increases. This fact is the rationale for the effectiveness of S56. In other words, in S56, the value of Δ1 suitable for the amount of PM accumulation is obtained by performing a modification that increases Δ1 as the PM accumulation amount B increases. Therefore, the damage determination in S140 and S150 becomes more precise.

  Next, Example 3 will be described. The third embodiment is the same as the second embodiment except that the flowchart of FIG. 4 in the second embodiment is replaced with FIG.

  In the third embodiment, the PM accumulation amount estimation B is incorporated into the DPF pressure guiding tube breakage detection process as in the second embodiment, and in this way, in the first embodiment, it is determined whether or not it is within a predetermined time by the timer. It is changed to determine whether or not the value of B has increased by a predetermined value or more. As a result, the upper limit of the interval between the two estimations is simply set according to the time, but the upper limit is changed according to the situation, so that more accurate damage determination is performed. Only parts of the third embodiment different from the second embodiment will be described below.

  In the flowchart of FIG. 5, S10, S20, S30, and S110 of FIG. 4 are deleted, and S95, S105, S115, and S116 are newly added. In essence, S115 is performed instead of S30, and it may be considered that S110 and S116 are the same. Since no timer is used, S10 and S20 related to the timer are deleted.

  In FIG. 5, the process proceeds to S95 after S90. In S95, the estimated value B obtained in S55 is stored in the variable PMB1. Since the first estimation is performed in S95, the process proceeds to S120 after S95, and the variable n is changed to 2, and the process is terminated. Further, after S100, the process proceeds to S105. In S105, the estimated value B obtained in S55 is stored in the variable PMB2, and then the process proceeds to S115.

  The time point of proceeding to S115 is after the second estimation, and both PMB1 and PMB2 are obtained. In S115, a difference between PMB2 and PMB1 is obtained, and it is determined whether this is equal to or less than a predetermined Δ2. If it is equal to or smaller than Δ2 (S115: YES), the process proceeds to S130. If it is greater than Δ2 (S115: NO), the process proceeds to S116. In S116, the variable n is returned to 1 and the process is terminated. After proceeding to S130, S130, S140, S150, and S160 are processed as in the first and second embodiments.

  The meaning of replacing S30 with S115 in the third embodiment will be described below. As a result of the determination in S115, the process proceeds to S116 when it is found by method B that the PM deposition amount has greatly increased between the two estimations.

  Therefore, even if S140 and S150 are performed and the difference in the PM deposition amount estimated value A is large and the process proceeds to S160, the difference may be a result of the PM continuously being deposited, not the pressure guiding tube breakage. . Therefore, the first estimation is also discarded and reset, and the first estimation is repeated. Therefore, in step S116, the variable n is returned to 1 and the process is terminated.

  On the other hand, the case where the process proceeds to S130 as a result of the determination in S115 is a case where it is found by Method B that the PM deposition amount has not increased so much between the two estimations. Therefore, when the difference in the PM deposition amount estimation value A is large, it can be considered that the difference is not a result of the PM continuously being deposited, but is a failure of the pressure guiding tube 10. Therefore, it progresses to S140 and S150 and performs damage determination.

  Basically, the case of proceeding to S116 above corresponds to the case where a predetermined time or more has elapsed in the first and second embodiments. Further, the case of proceeding to S130 above corresponds to the case where the time is still within a predetermined time in the first and second embodiments. FIG. 12 shows the relationship between Δ2 and the predetermined time. Depending on the operation state, the PM deposition amount may not increase much even after a sufficient time has elapsed, or the PM deposition amount may increase in a short time. Such a characteristic is lost when it is determined by simply using time whether it is a predetermined time or not, and the reliability of the determination in S140 and S150 is lowered. Therefore, by performing the PM accumulation amount estimation by the method B as in the third embodiment, the determination of S140 and S150 becomes more reliable.

  Next, Example 4 will be described. In the fourth embodiment, FIG. 3 in the first embodiment is replaced with FIG. 7, and FIG. 2 is replaced with FIG.

  In Example 1, it was determined only whether or not the pressure guiding tube 10 of the DPF 6 was broken, but in Example 4, the numerical value of the leakage amount is estimated. Furthermore, various controls are performed such as notifying the driver of the occurrence of leakage or controlling the operation corresponding to the leakage according to the amount of leakage. In the following, only the differences of the fourth embodiment from the first embodiment will be described.

  First, FIG. 6 shows a procedure of a leakage amount estimation process in the pressure guiding tube 10 of the DPF 6 in the fourth embodiment. In FIG. 2, S130, S140, S150, and S160 are deleted, and S180, S190, S200, and S210 are newly added.

  In FIG. 6, S170 is processed after S100. In S170, the amount of leakage (per unit time) from the pressure guiding tube 10 of the DPF 6 is estimated from VEX1, VEX2, and PM1-PM2 that have been obtained so far. The estimated value of the leakage amount may be stored in the ECU 9 in the form of a map, for example, and may be estimated in S170 using this.

  An example of the map is shown in FIG. In this example, there are a plurality of planes classified for different values of VEX1, and the plane has two coordinate axes VEX2 and PM1-PM2. Each plane is divided into meshes, and an estimated value of the leakage amount is obtained in advance corresponding to each area. What is necessary is just to obtain | require such a map by experiment, simulation, etc. corresponding to the apparatus structure to be used.

  Next, in S180, it is determined whether or not the leakage amount obtained in S170 is smaller than a predetermined value. In FIG. 6, this predetermined value is indicated by L1. When it is smaller than L1 (S180: YES), the amount of leakage is sufficiently small and it is determined that special control is not necessary, and the process is terminated. When it is L1 or more (S180: NO), the process proceeds to S190. In S190, it is determined whether or not the leakage amount obtained in S170 is smaller than a predetermined value different from the predetermined value in S180. In FIG. 6, this other predetermined value is indicated by L2. It is assumed that L2 is larger than L1 described above.

  When the amount of leakage is smaller than L2 (S190: YES), the process proceeds to S200. When the leakage amount is L2 or more (S190: NO), the process proceeds to S210. When the process proceeds to S200 or S210, the amount of leakage is large and it is considered that some notification or control is necessary. In particular, when proceeding to S210, the amount of leakage is larger than when proceeding to S200, and a more urgent response is required.

  For example, in S200, it is only necessary to notify the driver of the leak by turning on the warning lamp 14, change the EGR amount, change the injection pressure in the engine 2, or the like.

  The warning by the warning lamp 14 can warn the driver of the occurrence of leakage and prompt the driver to take appropriate measures. Further, in the change of the EGR amount, if the opening degree of the EGR valve 13 is lowered in a situation where the exhaust gas containing the particulate matter is leaking from the upstream side pressure guiding tube, the emission amount of the particulate matter from the internal combustion engine is suppressed. be able to. Thereby, the reduction of the exhaust purification performance due to leakage can be suppressed. Further, even when the injection pressure of the internal combustion engine is changed, the discharge of particulate matter from the internal combustion engine can be reduced. Therefore, it is possible to suppress a reduction in exhaust purification performance due to leakage.

  In S210, the fuel injection amount is limited such that at least one of the engine speed, the intake pressure, the intake amount, the exhaust pressure, the exhaust temperature, and the exhaust leakage amount is a predetermined value or less, and the regeneration of the DPF 6 is prohibited. Just do it.

  By setting at least one of the rotational speed, intake pressure, intake amount, exhaust pressure, exhaust temperature, and exhaust leakage amount of the internal combustion engine to a predetermined value or less, the exhaust amount from the internal combustion engine is suppressed, and as a result, particulate matter As a result, the deterioration of exhaust due to the influence of leakage is suppressed. Further, by prohibiting the regeneration of the particulate filter, it is possible to avoid further leakage in a state where the temperature is raised by the regeneration.

  Next, FIG. 7 will be described. In FIG. 7, S300 in FIG. 3 is replaced with S305 and S315, S310 is deleted, and S320 and S340 are replaced with S325 and S345. In the flowchart of FIG. 7, first, in S305, the amount of leakage from the pressure guiding tube 10 of the DPF 6 is estimated. This is the process of FIG. That is, in S305, the processing from S10 to S210 in FIG. 6 is performed.

  Next, in S315, it is determined whether or not the leakage amount obtained in S305 is zero. When the leakage amount is 0 (S315: NO), the process proceeds to S330 described above, and when the leakage amount is not 0 (S315: YES), the process proceeds to S325.

  In S325, the corrected PM accumulation amount estimation B is performed. As already described, in the PM accumulation amount estimation B, a map of the PM amount discharged from the engine 2 according to the operation state of the engine 2 is created, and this PM amount is integrated as the operation state progresses to obtain the PM accumulation amount. . At that time, the amount of PM discharged from the engine 2 is assumed to accumulate in the DPF 6 as it is.

In S325, in such PM accumulation amount estimation B, the amount excluding the amount of leakage from the pressure guiding tube 10 out of the PM amount discharged from the engine 2 is corrected to be the amount accumulated in the DPF 6. For this correction, for example, the following equation (E1) is used.
PMdpf = PMeng (VEX3-VEX4) / VEX3 (E1)

  In the formula (E1), PMdpf is the amount of PM deposited on the DPF 6, and PMeng is the amount of PM discharged from the engine 2. Further, as shown in FIG. 14, VEX3 is the flow rate of the exhaust gas flowing through the exhaust pipe 5 upstream of the pressure guiding tube 10, and VEX4 is the amount of exhaust gas leaking from the pressure guiding tube 10. For example, VEX3 may be an intake air amount.

  Obviously, the inflow gas flow rate to the DPF 6 is VEX3-VEX4. Therefore, the ratio of the inflow gas flow rate to the DPF 6 and the exhaust gas flow rate discharged from the engine 2 is (VEX3-VEX4) / VEX3. In the formula (E1), PMdpf is obtained by multiplying PMeng by this ratio. The above is the fourth embodiment.

  In the present invention, the internal combustion engine may be a diesel engine as in the above embodiment, but may be, for example, a lean burn gasoline engine. When a diesel engine is used as in the embodiment, it is possible to detect leakage from the upstream impulse tube 10 of the DPF 6 according to the present invention and to estimate the amount of leakage. It is.

  In the above embodiment, the DPF 6 constitutes a particulate filter. S50 constitutes a first estimation means. S40 constitutes a detection means. S140 and S150 constitute a determination means. Δ1 constitutes a predetermined threshold value. S55 constitutes a second estimating means. S56 constitutes a changing means. S300 and S320 constitute estimation method selection means. Δ2 constitutes a predetermined accumulation amount.

  S170 constitutes a leakage amount estimating means. S325 constitutes correction means. L1 constitutes a first predetermined leakage amount. L2 constitutes a second predetermined leakage amount. S200 constitutes a first control means. S210 constitutes a second control means.

The schematic diagram of the control device of the internal-combustion engine in the example of the present invention. 5 is a flowchart of DPF pressure guiding tube breakage detection processing according to the first embodiment. 3 is a flowchart of DPF regeneration timing determination processing in the first embodiment. 10 is a flowchart of a DPF pressure guiding tube breakage detection process in the second embodiment. 10 is a flowchart of a DPF pressure guiding tube breakage detection process in the third embodiment. 10 is a flowchart of DPF pressure guiding tube leakage amount estimation processing in the fourth embodiment. 10 is a flowchart of DPF regeneration timing determination processing according to the fourth embodiment. The figure which shows the relationship between intake air quantity and DPF passage gas flow rate. The figure which shows the relationship between exhaust gas flow volume and DPF differential pressure. The figure which shows the relationship between exhaust gas flow volume and DPF differential pressure. The figure which shows the relationship between DPF differential pressure and PM deposition amount (estimated value). The figure which shows the example of the time transition of PM deposition amount estimated value B. FIG. The figure which shows a leak amount estimated value map. The figure which shows the example of the leak of exhaust gas. The figure which shows the relationship between DPF differential pressure | voltage and exhaust gas flow volume. The figure which shows the log | history of a driving | running state.

Explanation of symbols

1 Control device 2 Diesel engine (internal combustion engine)
3 Intake pipe 4 Air flow meter 5 Exhaust pipe (exhaust passage)
6 Diesel particulate filter (DPF)
7 Differential pressure sensor 9 ECU
10 upstream pressure guiding pipe 11 downstream pressure guiding pipe 12 EGR passage 13 EGR valve 14 warning light 15 intake throttle valve

Claims (8)

The exhaust passage is formed of a particulate filter that collects particulate matter in the exhaust, an upstream pressure guiding tube that is a pipe formed from the inlet portion of the particulate filter, and an outlet portion of the particulate filter. A control apparatus for an internal combustion engine, comprising: a downstream pressure guiding pipe which is a pipe; and a differential pressure sensor for measuring a differential pressure which is a difference in pressure between the upstream pressure guiding pipe and the downstream pressure guiding pipe. ,
Detecting means for detecting an exhaust flow rate discharged from the internal combustion engine;
First estimation means for estimating a deposition amount of the particulate matter deposited on the particulate filter from the differential pressure measured by the differential pressure sensor and the exhaust flow rate detected by the detection means. ,
Two different times during operation of the internal combustion engine are defined as a first time and a second time, and the interval between the first time and the second time is within a predetermined time,
At the first time, the exhaust flow rate detected by the detection unit is set as a first flow rate, and the accumulation amount estimated by the estimation unit is set as a first estimated value.
At the second time, the exhaust flow rate detected by the detection unit is set as a second flow rate, and the accumulation amount estimated by the estimation unit is set as a second estimated value.
Assuming that the second flow rate is greater than the first flow rate,
And determining means for determining that there is a gas leak from the upstream pressure guiding tube when a difference between the first estimated value and the second estimated value is larger than a predetermined threshold value. Control device for internal combustion engine. Second estimating means for estimating the amount of particulate matter deposited on the particulate filter from the operating state of the internal combustion engine;
2. The control device for an internal combustion engine according to claim 1, further comprising a changing unit that increases the predetermined threshold value as the estimated value by the second estimating unit increases.   3. The method according to claim 2, further comprising an estimation method selection unit that estimates the amount of deposition using only the second estimation unit after the determination unit determines that there is a gas leak from the upstream pressure guiding tube. Control device for internal combustion engine. Second estimation means for estimating the amount of particulate matter deposited on the particulate filter from the operating state of the internal combustion engine;
2. The control device for an internal combustion engine according to claim 1, wherein the predetermined time is a time during which the estimated value of the accumulation amount estimated by the second estimation unit increases by a predetermined accumulation amount. In the exhaust passage, a particulate filter that collects particulate matter in the exhaust, an upstream pressure guiding tube formed from the inlet portion of the particulate filter, and a downstream guide formed from the outlet portion of the particulate filter. A control device for an internal combustion engine, comprising: a pressure pipe; and a differential pressure sensor for measuring a differential pressure that is a difference in pressure between the upstream side pressure guiding pipe and the downstream side pressure guiding pipe,
Detecting means for detecting an exhaust flow rate discharged from the internal combustion engine;
First estimation means for estimating a deposition amount of the particulate matter deposited on the particulate filter from the differential pressure measured by the differential pressure sensor and the exhaust flow rate detected by the detection means. ,
Two different times when the internal combustion engine is operating are defined as a first time and a second time, and an interval between the first time and the second time is within a predetermined time,
At the first time, the exhaust flow rate detected by the detection unit is set as a first flow rate, and the accumulation amount estimated by the estimation unit is set as a first estimated value.
At the second time, the exhaust flow rate detected by the detection unit is set as a second flow rate, and the accumulation amount estimated by the estimation unit is set as a second estimated value.
Assuming that the second flow rate is greater than the first flow rate,
Leakage amount estimating means for estimating a leak amount of gas from the upstream pressure guiding tube from the first flow rate, the second flow rate, and the difference between the second estimated value and the first estimated value. A control apparatus for an internal combustion engine, comprising: Second estimating means for estimating the amount of particulate matter deposited on the particulate filter from the operating state of the internal combustion engine;
6. A correction unit that corrects the estimated value of the accumulation amount estimated by the second estimation unit from the second flow rate and the leakage amount estimated by the leakage amount estimation unit. The control apparatus of the internal combustion engine described in 1. A warning light for warning,
EGR for exhaust gas recirculation,
When the leakage amount estimated by the leakage amount estimation means is larger than a first predetermined leakage amount, at least one of lighting of the warning lamp, changing the EGR amount, or changing the injection pressure of the internal combustion engine The control device for an internal combustion engine according to claim 5, further comprising first control means for performing the operation.   When the leakage amount estimated by the leakage amount estimation means is larger than a second predetermined leakage amount that is larger than the first predetermined leakage amount, the rotational speed, intake pressure, intake amount, exhaust pressure, exhaust gas of the internal combustion engine The control apparatus for an internal combustion engine according to claim 7, further comprising second control means for setting at least one of a temperature and an exhaust leak amount to a predetermined value or less, or prohibiting regeneration of the particulate filter.

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